The invention relates to a method for operation of a motor vehicle alarm system in accordance with the preamble of claim 1.
A method of this type is known from EP 0 105 774.
Motor vehicles are generally secured against theft by alarm systems that watch over door contacts, current loops and the vehicle interior. If an alarm is triggered, a central control unit--the "alarm center"--either actuates signal devices such as horn, hazard warning light or headlamp flasher (passive methods), or prevents starting of the vehicle or engine control system (active methods). However, these passive and active methods cannot provide effective protection of the vehicles, since all the effects of the alarm can easily be neutralized--particularly by professional car thieves--by deactivating or disabling the alarm system.
In the generic publication EP 0 105 774 mentioned at the outset, the alarm system's central control unit, connected unidirectionally to various control units of the motor vehicle, is accommodated inaccessibly inside the vehicle (for example inside the engine-transmission assembly, the transmission or the vehicle chassis); since the central control unit can only be removed and replaced at very great expense, relatively effective albeit expensive theft protection is ensured.